Everybody can guess and conjecture, but unless an official statement is issued by either Nvidia, AMD or TSMC, it's just a rumour.

As far as any of us know, Nvidia's product launch and production ramp up is progressing according to their latest schedule.

EDIT:

That being said, if the rumour is true, that really sux. kepler wouldn't be available anytime soon, and prices would remain high for AMD's current stock of cards. Really, the people who would lose out would be Nvidia, and the consumer, while AMD would probably benefit.

"Unfortunately for Nvidia, yields of chips made using 28nm process technology at TSMC, including Kepler, are lower than the company originally anticipated and therefore their costs are high and Nvidia's chief executive recently complained that the company cannot get enough wafers."

meh, it's not new news that the they are hitting roadbumps with the 28nm fab space being very tight atm. they've been saying that for a few months that it will cause some higher prices and smaller stock as it is currently not producing at a high enough volume.

TSMC did hit what's called a "show stopper" problem in manufacturing. I can't discuss it more than that.

However, AMD will be hurt just as much as NVIDIA, or more. Now that Kepler production has ramped up, the lion's share of TSMC's 28nm HP production has shifted away from AMD's parts since NVIDIA has reserved far more production capacity than their competitor. That's why AMD's HD 7970 and HD 7950 suddenly became VERY hard to find a few weeks ago and will likely remain in short supply for the foreseeable future, even before the ramp-down affected channel availability.